J. a. Cooke — Section in Middle Lias, Lincoln. 2-j7 



weathering it exhibits many iron stains. In places it passes into 

 a typical ironstone rock, or is sandwiched between two thin layers 

 of iron-pyrites, both of which have imbedded in them representatives 

 of all the fossils that are to be found, either in the limestone 

 course or in the subjacent and superposed clays and shales. More 

 fossils are to be obtained from these pyritic layers than from any 

 other, part of the formation. 



Foraminifera are most abundant, and a considerable part of the 

 bed is made up of the tests of Bairdia liassica, and oolitic grains 

 of oxide of iron of the size and appearance of millet-seed. Referring 

 to this bed, which was then very imperfectly exposed in Glaisiers 

 Pit, Mr. W. D. Carr described it as a "soft ferruginous, clayey 

 sandstone, with occasional casts of shells that do not help in de- 

 termining the hoi'izon." I have before referred to the finding 

 of A. margaritatus in it, in abundance, by the Rev. E. Nelson and 

 myself. 1 also obtained from it R. tetrahedra, which would seem at 

 once to determine its equivalence with the Marlstone, that has 

 hitherto been supposed to have been missing in this neighbourhood. 



The septaria in 22, 24, and 28 vary considerably from those in 

 other parts of the section. They are smooth, depressed, spheroidal 

 masses of hard claystone. Most of them contain specular iron. 

 Incipient fracture lines that extend partially throughout their mass, 

 and that exhibit in their fractured facets layers of powdery, ferrous 

 oxide, are a common feature. 



As a rule the fossils are found attached to the exterior of the 

 nodule, and are frequently filled with calcite ; but A. margaritatus 

 and A. spinatus are more frequently found within and forming the 

 nucleus of the nodule. 



Another intei-esting characteristic of the two septarian layers 24 

 and 28 is the abundance of phosphatic nodules that are contained 

 in them. These nodules are smooth, polished masses of phosphates 

 of lime and alumina, and they vary in size from a small pea to a 

 walnut. They are of all shapes — some being symmetrically elliptical, 

 oval, and circular, whilst others are most irregular in outline. In 

 colour thej^ are uniformly of a light chocolate colour. Sections under 

 the microscope showed that nearly all of them have a nucleus of 

 organic matter; sometimes a shell fragment, but most frequently 

 it consists of the tests of Foraminifera — Cristellaria, Nodosaria, 

 and Lagena. 



Immediately beneath the limestone course 26 is an irregular seam 

 of light-blue shaly clay (27), of a marked micaceous and ferruginous 

 aspect. It is chiefly remarkable for the enormous numbers of 

 Belemnites [B. clavatus, B. vulgaris, and B. longiformis) that it 

 contains. In some places they are so thick that the bed is almost 

 entirely made up of them. 



The line of junction between these Belemnite shales and the lime- 

 stone is also extremely pi'olific in molluscan remains. Shells and 

 casts of Astarte, Lima, Cardinia, Gresslya, Pecten, Nuctda occur in 

 masses with other, though less numerous, shells of Eucyclus, Euiima, 

 Cerithium, Ostrea, Plicatula, and Modiola. 



DBCADE IT. VOL. IV. NO. VI. 17 



